Composition having alkaline ph and process for forming superconformation therewith

ABSTRACT

A composition includes a solvent; a metal ion disposed in the solvent; an accelerator disposed in the solvent; and a suppressor disposed in the solvent, a pH of the composition being alkaline and effective to form a superconformation comprising a damascene deposit that includes an electrochemically reduced form of the metal ion. A process for forming a superconformation includes: contacting a substrate with a composition, the composition including: a solvent; a metal ion disposed in the solvent; an accelerator disposed in the solvent; and a suppressor disposed in the solvent; controlling a pH of the composition to be alkaline; and producing a damascene deposit on the substrate to form the superconformation, the damascene deposit including an electrochemically reduced form of the metal ion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/194,320 filed Jul. 20, 2015, the disclosure of which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with United States government support from the National Institute of Standards and Technology. The government has certain rights in the invention.

BRIEF DESCRIPTION

Disclosed is a composition including: a solvent; a metal ion disposed in the solvent; an accelerator disposed in the solvent; and a suppressor disposed in the solvent, a pH of the composition being alkaline and effective to form a superconformation including a damascene deposit that comprises an electrochemically reduced form of the metal ion.

Further disclosed is a process for forming a composition, the process including: disposing a metal ion in a solvent; disposing an accelerator in the solvent; disposing a suppressor in the solvent; and adjusting a pH of the composition to be alkaline and effective to form a superconformation including a damascene deposit that comprises an electrochemically reduced form of the metal ion.

Additionally disclosed is a process for forming a superconformation, the process including: contacting a substrate with a composition, the composition including: a solvent; a metal ion disposed in the solvent; an accelerator disposed in the solvent; and a suppressor disposed in the solvent; controlling a pH of the composition to be alkaline; and producing a damascene deposit on the substrate to form the superconformation, the damascene deposit including an electrochemically reduced form of the metal ion.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike.

FIG. 1A and FIG. 1B show an article that includes a superconformation;

FIG. 2 shows a composition to form a superconformation disposed on a substrate;

FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D show an article that includes a superconformation;

FIG. 4A and FIG. 4B show an article that includes a superconformation;

FIG. 5 shows an article that includes a superconformation;

FIG. 6A and FIG. 6B show a graph of current density versus potential;

FIG. 7A, FIG. 7B, and FIG. 7C show a graph of current density versus time;

FIG. 8A and FIG. 8B show a graph of current density respectively versus time or offset time;

FIG. 9 shows a graph of current density versus time; and

FIG. 10A, FIG. 10B, FIG. 10C, and FIG. 10D show an article that includes a superconformation.

DETAILED DESCRIPTION

A detailed description of one or more embodiments is presented herein by way of exemplification and not limitation.

It has been discovered that a composition herein provides production of a superconformation that includes a metal disposed on a substrate in a presence of an electric potential for an oxidation-reduction reaction. The oxidation-reduction reaction involves reducing a metal ion in the composition to form a damascene deposit on the substrate. Further, the composition includes a suppressor or accelerator to form the superconformation in a presence of an alkaline pH of the composition. Additionally, the superconformation has a bottom fill, side fill, and corner fill in an absence of a void or seam of the superconformation.

In an embodiment, as shown in FIG. 1A, article 2 (shown in cross-section) includes superconformation 4 disposed on substrate 6. Substrate 6 includes first surface 8 that has a surface contour formed by top surface 9 and trench 12. With respect to y-z coordinates shown as an inset in FIG. 1A, trench 12 includes bottom wall 16 and a plurality of side walls 14 to contact bottom wall 16 at corner 18 and to extend (in a positive z-direction with respect to bottom wall 16) from corner 18 toward top surface 9. A shape of trench 12 or bottom wall 16 can be any shape effective to produce superconformation 4 by electrodeposition of metal on substrate 6. Further, trench 12 has first width W and height H in the y-z plane. In some embodiments, trench 12 has second width W2 in a direction orthogonal to the y-z plane, wherein first width W and second width W2 can be a same length or a different length.

Superconformation 4 is disposed on substrate 6 at interface 10 and extends to second surface 20. Superconformation 4 includes bottom fill 28 disposed proximate to bottom wall 16 of trench 12, side fill 29 disposed proximate to side wall 14 of trench 12, corner fill 26 disposed proximate to corner 18 of trench 12, and bump 24 disposed proximate to top surface 9 of trench 12. In some embodiments, as shown in FIG. 1B, superconformation 4 includes over fill 22 disposed proximate to bottom fill 28 and at a z-position higher than top surface 9.

Substrate 6 can include a material on which superconformation 4 can be produced by disposing a metal from electrochemically reducing a metal ion. Exemplary substrates include a metal, semiconductor, plastic, insulator, and the like. In an embodiment, substrate 6 is the semiconductor such as silicon, gallium nitride, and the like or a compound semiconductor. In some embodiment, substrate 6 is the insulator such as silicon dioxide.

To produce superconformation 4, an intermediate layer that can include seed layer 44 (see FIG. 2) can be disposed on substrate 6 on which to form superconformation 4. The intermediate layer and seed layer 44 can include a seed to form the metal included in superconformation 4. Seed layer 44 can be a layer of metal, e.g., copper, disposed on a diffusion barrier in trench 12 to facilitate complete filling of trench 12 with the metal in superconformation 4. Exemplary seed metals include a transition metal such as an element from group 3 to group 12 of the periodic table, or a combination thereof. In a particular embodiment, the seed is an element from group 9, group 10, or group 11, specifically, group 11, and more specifically copper, silver, or a combination thereof. In some embodiments, the intermediate layer includes cobalt, manganese, or the like.

In an embodiment, superconformation 4 is a damascene deposit that includes the metal. The metal can be the transition metal included in seed layer 44 or independently an element from group 3 to group 12 of the periodic table, or a combination thereof. In a particular embodiment, the metal is an element from group 9, group 10, or group 11, specifically, group 11, and more specifically copper, silver, or a combination thereof.

Superconformation 4 is formed from composition 30. As shown in FIG. 2, composition 30 can be disposed on substrate 6 with seed layer 44 optionally interposed composition 30 and substrate 6. In an embodiment, composition 30 includes solvent 32, metal ion 34 disposed in solvent 32, accelerator 38 disposed in solvent 32, and suppressor 36 disposed in solvent 32. Here, a pH of composition 30 is alkaline and effective to form superconformation 40 that includes the damascene deposit that includes a metal that is an electrochemically reduced form of metal ion 34. Complex 40 can be present in composition 30 and can include metal ion 34 in contact with suppressor 36. In complex 40, metal ion 34 can be bonded or electrostatically attracted to suppressor 36. Without wishing to be bound by theory, it is believed that metal ion 34, suppressor 36, accelerator 38, or complex 40 can be disposed on seed layer 44 as adsorbate 42, which is shown in FIG. 2 as accelerator 38 disposed on seed layer 44.

Additionally, without wishing to be bound by theory, it also is believed that superconformation 4 is formed by contacting seed layer 44 with metal ion 34, which is reduced thereon to form the metal disposed on substrate 6 as the damascene deposit. Production of superconformation 4 is accomplished by adsorption of suppressor 36 or accelerator 38 on seed layer 44 as metal ion 34 is reduced to form the metal. Here, adsorption of suppressor 36 can compete with adsorption or desorption of accelerator 38 to provide a rate of formation of the metal from metal ion 34 and rate of formation of superconformation 4 on substrate 6.

The metal of superconformation 4 can be a same element or combination elements from reduction of metal ion 34, e.g., the transition metal. Exemplary metal ions 34 include copper (e.g., Cu⁺ or Cu²⁺), A_(g) ⁺, Pb²⁺, Au', or a combination thereof. In a particular embodiment, metal ion 34 is Cu²⁺, and the metal of superconformation 4 is copper.

Metal ion 34 can be provided to composition 30 from a source such as a metal salt, complex, and the like. As used herein, the term “complex” refers to a metal ion associated (e.g., bonded or electrostatically attracted) with a ligand. The complex can be neutral or charged, e.g., in a complex ion such as [Ag(CN)_(2]) ⁻. The metal salt can include metal ion 34 and an anion. The anion can be monoatomic anion or polyatomic anion. Exemplary anions include sulfate, halide, nitrate, fluoroborate, alkylsulfonate, arylsulfonate, sulfamate, gluconate, cyanide (CN⁻), and the like, or a combination thereof. Further, the metal ion source can include a metal sulfate, metal halide, metal acetate, metal nitrate, metal fluoroborate, metal alkylsulfonate, metal arylsulfonate, metal sulfamate, metal gluconate, and the like. In an embodiment, the metal is copper. A suitable source of copper ions include, e.g., copper sulfate, copper chloride, copper acetate, copper nitrate, copper fluoroborate, copper methane sulfonate, copper phenyl sulfonate, copper phenol sulfonate, copper p-toluene sulfonate, copper sulfate pentahydrate, and the like.

The ligand can have be charged (e.g., a cation, anion, or zwitterion) or neutral. It will be appreciated that the ligand can be a monodentate ligand or multidentate ligand with a denticity of the ligand not limited to being bidentatate, tridentate, quadradentate, pentadentate, and the like. For example, ethylenediaminetetraacetic acetate (EDTA) can bind nitrogen and oxygen atoms to metal ion 34, with alkyl groups bridging these atoms. In some embodiments, a plurality of ligands can be complexed to metal ion 34.

According to an embodiment, the ligand includes a group such as a halide, an amide, an η²-alkene, CO, CS, CO₂, CN, an amine, a nitrile, an isocyanide, a phosphane, an alkylidene, an alkyldiide, a nitrene, an imide, an oxide, an alkylidyne, an alkyltriide, an η³-allyl, an η³-enyl, an η³-cyclopropenyl, NO, an η⁴-diene, an η⁴-cyclobutadiene, an η⁵-cyclopentadienyl, an η⁶-arene, an η⁶-triene, an η⁷-tropylium, an η⁷-cycloheptatrienyl, an η⁸-cyclooctatetraene, or a combination thereof.

In a certain embodiment the ligand is the aminocarboxylic acid. Exemplary aminocarboxylic acids include alanine; 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid; 1,4,7,10,-tetraazacyclododecane-N,N′,N″-triacetic acid; 2,2′,2″,2′″-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid; diethylenetriaminepentaacetic acid; ethylenediamine-N,N′-bis(2-hydroxyphenylacetic acid); ethylenediaminetetraacetic acid; ethylene-bis(oxyethylenenitrilo)tetraacetic acid; 2-{6-[bis(carboxymethyl)amino]-5-(2-{2-[bis(carboxymethyl)amino]-5-methylphenoxy}ethoxy) -1-benzofuran-2-yl}-1,3-oxazole-5-carboxylic acid; N,N′-di(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid; (hydroxyethyl)ethylenediaminetriacetic acid; 1,4,7-tris(carboxymethyl)-10-(2′-hydroxy)propyl)-1,4,7,10-tetraazocyclodecane; iminodiacetic acid; 2-[4-(bis(carboxymethyl)amino)-3-[2-[2-(bis(carboxymethyl)amino)-5-methylphenoxy]ethoxy]phenyl]-1H-indole-6-carboxylic acid; (methylimino)diacetic acid; 2,2′,2″-(1,4,7-triazanonane-1,4,7-triyl)triacetic acid; nitrilotriacetic acid; 2,2′,2″, 2′″-(1,4,8,11-tetraazacyclotetradecane-1,4,8,11-etrayl)tetraacetic 3,6,9,12-acid; tetrakis(carboxymethyl)-3,6,9,12-tetra-azatetradecanedioic acid; a derivative thereof; a salt thereof; or a combination thereof.

In one embodiment, the ligand is the lactate, malate, citrate, amincarboxylic acid listed above, or a combination thereof. According to an embodiment, the ligand includes an aliphatic amine, aliphatic hydroxylamine, and the like. Exemplary amines include ethylenediamine, diaminopropane, diaminobutane, N,N,N,N-tetramethyldiaminomethane, diethylenetriamine, 3,3-aminobispropylamine, triethylene tetramine, monoethanolamine, diethanolamine, triethylanolamine, N-methyl hydroxylamine, 3-amino-1-propanol, N-methyl ethanolamine, and the like.

In an embodiment, complex 40 includes metal ion 34 and the ligand in a metal-ligand complex (indicated as “metal-ligand” or “ligand-metal”) such as metal-acetylacetonate, metal-triethanolamine, metal-lactate, di(ammonium lactate)-metal, metal-citrate, metal-malate, metal-EDTA complex, metal-BAPTA complex, metal-DCTA complex, metal-DO3A complex, metal-DTPA complex, metal-EGTA complex, metal-HBED complex, metal-HEDTA complex, metal-HP-DO3A complex, metal-indo-1 complex, metal-NOTA complex, metal-TETA complex, metal-TTHA complex, or a combination thereof.

In some embodiments, the ligand includes a functional group that includes hydrogen, alkyl, alkoxy, fluoroalkyl, cycloalkyl, heterocycloalkyl, cycloalkyloxy, aryl, aralkyl, aryloxy, aralkyloxy, heteroaryl, heteroaralkyl, alkenyl, alkynyl, NH₂, amine, alkyleneamine, aryleneamine, alkenyleneamine, and hydroxyl. In a particular embodiment, the ligand includes an aminocarboxylic acid, a lactate, a malate, a citrate, or a combination thereof.

In composition 30, metal ion 34 is disposed in solvent 32. Suitable solvents will be effective to dissolve disperse metal ion 34, suppressor 36, accelerator 38, or complex 40. The solvent can be readily removed after formation of superconformation 4. Exemplary solvents include water, alcohol (ethanol, methanol, propanol, and the like), tetrahydrofuran, toluene, acetone, dimethylformamide, and the like. In a particular embodiment, solvent 32 is water. A resistivity of the solvent can be effective to not interfere with formation of superconformation 4 and can be, e.g., 18 MΩ cm.

The pH of composition 30 is alkaline. It will be appreciated that conventional processes for forming a damascene deposit are performed at an acidic pH and typically in a presence of an acid. Here, reduction of metal ion 34 to the metal of superconformation 4 surprisingly occurs in the alkaline pH of composition 30 because conventional additives used to deposit metal are effective in an acidic medium but are ineffective in the alkaline pH. In an embodiment, the pH of composition 30 is controlled to be alkaline. As used herein, “alkaline” or “alkaline pH” refers to a pH greater than 7. Reducing metal ion 34 and forming superconformation 4 can be achieved by controlling the pH to be greater than 8, specifically greater than 9, more specifically greater than 10, further specifically from 10 to 14, and more further specifically from 10 to 12.

In various embodiments, a pH control agent such as a hydroxyl ion releasing agent or a buffering agent is introduced to composition 30 to achieve the alkaline pH. Exemplary hydroxyl ion releasing agents include a soluble or partially soluble hydroxide or carbonate that provides the desirable alkaline pH value in composition 30. An alkali hydroxide, e.g., sodium hydroxide, or carbonate can be used. Other materials include, e.g., NH₄OH, Ca(OH)₂, Mg(OH)₂, Bi(OH)₃, Co(OH)₂, Pb(OH)₂, Ni(OH)₂, Ba(OH)₂, Sr(OH)₂, tetramethyl ammonium hydroxide, triethanolamine, monoethanolamine, and the like. It is contemplated that introducing such material can precipitate in an alkaline pH. In some embodiments, an amount of the pH control agent is less than an amount that would cause the pH control agent to form a precipitate in the solvent. The amount of the hydroxyl ion source is that which is sufficient to yield the pH value of composition 30 to be pH to be greater than 8, specifically greater than 9, more specifically greater than 10, further specifically from 10 to 14, and more further specifically from 10 to 12.

Without wishing to be bound by theory, it is believed that suppressor 36 adsorbs to substrate 6, seed layer 44, and the like to slow kinetically the reduction of metal ion 34 or to increase a local polarization of substrate 6 at a location where suppressor 36 is present relative to a location where suppressor 36 is absent. In an embodiment, suppressor 36 includes a polymer, the ligand (described above), a halide, or a combination thereof. The polymer can include a functional group that is a hydroxyl, sulfhydryl, carbonyl, amine, imine, amide, carboxyl, phosphate, sulfate, phenyl, halo, aldehyde, haloformyl, cyanate, nitrate, nitro, borono, or a combination thereof. Exemplary polymers for suppressor 36 include a polyalkene glycol (e.g., polyethylene oxide, polypropylene oxide, polyethylene glycol, polypropylene glycol, and the like), polyethylene or polypropylene oxide with a S- or N-containing functional groups, block polymer of polyethylene oxide or polypropylene oxide, polyether, carbohydrate, surfactant, and the like. Suppressor 36 can have a linear chain structure or branch structure. In an embodiment, suppressor 36 includes a halide such as chloride, bromide, or iodide.

In an embodiment, suppressor 36 includes a nitrogen or sulfur atoms. Suppressor 36 can be a compound having the formula R₂N-C(S)Y, wherein each R is independently hydrogen or an alkyl, alkenyl, or aryl group, and Y is XR¹, NR₂ or N(H)NR₂ where X is O or S, and R¹ is hydrogen or an alkali metal. Examples of such a compound includes a thiourea, thiocarbamate, or thiosemicarbazide.

The thiourea compound can have the formula (R₂N)₂CS, wherein each R is independently hydrogen or an alkyl, cycloalkyl, alkenyl, or aryl group. The alkyl, cycloalkyl, alkenyl, or aryl group can include a plurality, e.g., four or more, of carbon atoms and substituents such as a hydroxy, amino, or halogen group. The alkyl and alkenyl group can be straight chain or branched. The thiourea compound includes homologues or analogs thereof. Exemplary thiourea compounds include thiourea; 1,3-dimethyl-2-thiourea; 1,3-dibutyl-2-thiourea; 1,3-dietyl-2-thiourea; 1,3-diethyl-2-thiourea; 1,1-diethyl-2-thiourea; 1,3-diheptyl-2-thiourea; 1,1-diphenyl-2-thiourea; 1-ethyl-1-(1-naphthyl)-2-thiourea; 1-ethyl-1-phenyl-2-thiourea; 1-ethyl-3-phenyl-2-thiourea; 1-phenyl-2-thiourea; 1,3-diphenyl-2-thiourea; 1,1,3,3-tetramethyl-2-thiourea; 1-allyl-2-thiourea; 3-allyl-1,1-diethyl-2-thiourea; 1-methyl-3-hydroxyethyl-2-thiourea; 2,4-dithiobiuret; 2,4,6-trithiobiuret; alkoxy ether of isothiourea; and the like.

The thiocarbamate compound can have the formula R₂NC(S)-XR¹, wherein each R is independently hydrogen, or an alkyl, alkenyl, or aryl group, X is O or S, and R¹ is hydrogen or an alkali metal. The alkyl and alkenyl groups can include, e.g., from 1 to 5 carbon atoms. In some embodiments, the alkyl groups can include 1 or 2 carbon atoms. In another embodiment, both R groups are alkyl groups containing 1 or 2 carbon atoms. Exemplary thiocarbamate compounds include dimethyl dithiocarbamic acid, diethyl dithiocarbamic acid, sodium dimethyldithiocarbamate hydrate, sodium diethyldithiocarbamate trihydrate, and the like.

The thiosemicarbazide compound can have the formula R₂N-C(S)-N(H)NR₂, wherein each R is independently hydrogen or an alkyl, alkenyl, or aryl group. In an embodiment, the R groups are alkyl groups that include from 1 to 5 carbon atoms. In another embodiment, the alkyl groups each contain 1 or 2 carbon atoms. Exemplary such thiosemicarbazide compounds include 4,4-dimethyl-3-thiosemicarbazide and 4,4-diethyl-3-thiosemicarb azide.

According to an embodiment, suppressor 36 includes a nitrogen-containing disulfide having the formula (R₂NCS₂)₂, wherein each R is independently hydrogen, or an alkyl, alkenyl, or aryl group. The alkyl groups can include from 1 to 5 carbon atoms. In another embodiment, the alkyl groups can include one or two carbon atoms. In some embodiments, both R groups are alkyl groups that include one or two carbon atoms. Exemplary organic disulfides include bis(dimethylthiocarbamyl) disulfide(thiram) bis(diethylthiocarbamyl) disulfide, and the like.

Suppressor 36 also can include a nitrogen-containing heterocyclic compound that is substituted or unsubstituted. Exemplary substituents include an alkyl group, aryl group, nitro group, mercapto group, and the like. The nitrogen-containing heterocyclic compound can include a nitrogen atom. Exemplary nitrogen-containing heterocyclic compounds include a pyrrole, imidazole, benzimidazole, pyrazole, pyridine, dipyridyl, piperazine, pyrazine, piperidine, triazole, benzotriazole, tetrazole, pyrimidine, and the like. The nitrogen-containing heterocyclic compounds also can include an atom such as oxygen or sulfur. Exemplary heterocyclic compounds containing nitrogen or oxygen include morpholine, and exemplary nitrogen-containing heterocyclic compounds that include nitrogen and sulfur are rhodanines, thiazoles, thiazolines, thiazolidines, and the like.

In an embodiment, suppressor 36 includes the above-described nitrogen-containing heterocyclic compounds that are substituted with a mercapto group. Exemplary mercapto substituted nitrogen-containing heterocyclic compounds include 2-mercapto-1-methyl imidazole; 2-mercaptobenzimidazole; 2-mercaptoimidazole; 2-mercapto-5-methyl benzimidazole; 2-mercaptopyridine; 4-mercaptopyridine; 2-mercaptopyrimidine (2-thiouracil); 2-mercapto-5-methyl-1,4-thiadiazole; 3-mercapto-4-methyl-4H-1,2,4-triazole; 2-mercaptothiazoline, 2-mercaptobenzothiazole, 4-hydroxy-2-mercaptopyrimidine; 2-mercaptobenzoxazole; 5-mercapto-1-methyltetrazole; 2-mercapto-5-nitrobenzimidazole; and the like.

According to an embodiment, suppressor 36 includes an alkali metal thiocyanate such as sodium thiocyanate or potassium thiocyanate. A thio alcohol can be included as suppressor 36. Examples include 3-mercapto ethanol; 6 mercapto-1-hexanol; 3-mercapto-1,2-propanediol; 1-mercapto-2-propanol; 3-mercapto-1-propanol; mercaptoacetic acid; 4-mercaptobenzoic acid salt; 2-mercaptopropionic acid salt; and 3-mercaptopropionic acid salt.

Various other non-limiting examples of suppressor 36 include dodecyltrimethylammonium chloride; dodecyltrimethylammonium bromide; sodium dodecyl sulfate; 2-butyne-1,4-diol; saccharin; sodium benzenesulfonate; cetyltrimethylammonium chloride; polyethyleneimine (e.g., 1800 molecular weight (Mw)); 4-picoline; polyethylene glycol (e.g., 3400 Mw); and the like.

Composition 30 also includes accelerator 38 to accelerate growth of superconformation 4 on substrate 6. Without wishing to be bound by theory, it is believed that accelerator 30 locally reduces a polarization of substrate 6 caused by presence of suppressor 36. Accordingly, it is believed that accelerator 38 locally increases a deposition rate of the metal from metal ion 34 to form superconformation 4. Reduction of the polarization of substrate 4 occurs most markedly in a location that accelerator 38 adsorbs and is present in highest surface coverage. It is contemplated that accelerator 38 may become adsorbed (e.g., chemisorbed) to substrate 6 and immobile, but accelerator 38 may not be incorporated into the superconformation 4 so that accelerator 38 remain present on second surface 20 of superconformation 4 as metal is disposed on substrate 6 from metal ion 34. As trench 12 is filled with the metal, the local surface coverage of accelerator 38 increases within trench 12.

Accelerator 38 can include an inorganic compound selected to increase the deposition rate of the metal from metal ion 34 in composition 30 and optionally to decrease gas (e.g., hydrogen) evolution that might otherwise create a defect (e.g., a pore) in superconformation 4. Exemplary accelerators 38 include dimercaptopropane sulfonic acid salt, dimercaptoethane sulfonic acid salt, mercaptopropane sulfonic acid salt, mercaptoethane sulfonic acid salt, bis-(3-sulfopropyl) disulfide, a derivative thereof, and the like. Inorganic compounds include selenium-containing anions (e.g., SeO₃ ²⁻, SeO₄ ²⁻, SeCN⁻, SeO₂ ²⁻, SeO₃ ⁻, SeNC⁻, and the like), tellurium-containing anions (e.g., TeO₃ ^(2'), Te²⁻, and the like), or a combination thereof.

In an embodiment, composition 30 includes ethylenediaminetetraacetic acid, cupric sulfate, and potassium selenocyanate at a pH of 12.0 through inclusion of sodium hydroxide.

Other components (e.g., a leveler, surfactant, and the like) can be present in composition 30 to provide desired characteristics, provided that such components do not significantly or adversely affect the formation of superconformation 4.

The leveler can be included in composition 30 to inhibit growth of superconformation 4, to reduce interaction between suppressor 36 and accelerator 38, or to control deposition rate enhancement provided by accelerator 38. The leveler can include a nitrogen atom, amine, imide, or imidazole, sulfur functional group, and the like. Certain levelers include a five- or six-membered ring or conjugated organic compound derivative. A nitrogen group can be in a ring structure of the leveler. In amine-containing levelers, the amine can be a primary, secondary or tertiary alkyl amine; aryl amine; or a heterocyclic amine. Exemplary amines include dialkylamines, trialkylamines, arylalkylamines, triazoles, imidazole, triazole, tetrazole, benzimidazole, benzotriazole, piperidine, morpholines, piperazine, pyridine, oxazole, benzoxazole, pyrimidine, quonoline, or isoquinoline.

The leveler also can include an ethoxide group. In some embodiments, the leveler include a backbone similar to that found in polyethylene glycol or polyethyelene oxide such that fragments of amine functionally are inserted over the backbone. Exemplary epoxides include an epihalohydrins (e.g., epichlorohydrin or epibromohydrin) or a polyepoxide compound (e.g., a polyepoxide compounds having a plurality of epoxide moieties joined by an ether-containing linkage). Exemplary polymeric leveler compounds include a polyethylenimine, polyamidoamine, polyvinylpyrrolidone, and the like. An exemplary non-polymeric leveler includes 6-mercapto-hexanol.

A surfactant can be included in composition 30 and can be, e.g., an amine (e.g., an ethoxylated amine, polyoxyalkylene amine, or alkanol amine); amide; polyglycol-type wetting agent (e.g., a polyethylene glycol, polyalkylene glycol, or polyoxyalkyene glycol); high molecular weight polyether; polyethylene oxide (e.g., Mw from 100,000 to 3 million); block copolymer of polyoxy-alkyene; alkylpolyether sulfonate salt; complexing surfactant such as alkoxylated diamines; and the like.

In composition 30, an amount of metal ion 34 present is the amount sufficiently to produce superconformation 4. In an embodiment, metal ion 34 is present in an amount from 1 millimoles per liter solvent (mmol/L) to 100 mmol/L, specifically from 20 mmol/L to 40 mmol/L.

In composition 30, an amount of suppressor 36 present is an amount to sufficiently suppress formation of superconformation 4. In an embodiment, suppressor 34 is present in an amount from 1 mmol/L to 500 mmol/L, specifically from 10 mmol/L to 40 mmol/L.

In composition 30, an amount of accelerator 38 present is an amount to sufficiently accelerate formation of superconformation 4. In an embodiment, accelerator 38 is present in an amount from 0.5 micromoles per liter of solvent (μmol/L) to 50 μmol/L, specifically from 0.5 μmol/L to 4 μmol/L.

Seed layer 44 is formed on substrate 6 with a thickness to enables formation of superconformation 4 from metal ion 34 in composition 30. The thickness of seed layer 44 can be from 1 nm to 200 nm, specifically from 20 nm to 120 nm.

In an embodiment, a process for forming composition 30 includes disposing metal ion 34 in solvent 32; disposing accelerator 38 in solvent 32; disposing suppressor 36 in solvent 32; and adjusting a pH of composition 30 to be alkaline and effective to form superconformation 4 that includes the damascene deposit, which includes the metal (an electrochemically reduced form of metal ion 34). In a certain embodiment, the pH of composition 30 is greater than or equal to 12 after adjusting the pH.

According to an embodiment, a process for forming superconformation 4 includes contacting substrate 6 with composition 30; controlling the pH of composition 30 to be alkaline; and producing a damascene deposit on substrate 6 to form superconformation 4. Here, the damascene deposit includes an electrochemically reduced form of metal ion 34. The process further includes disposing an electrode in the composition; subjecting substrate 6 to a first potential; and subjecting the electrode to a second potential. Additionally, the process includes controlling a potential difference between the first potential and the second potential; controlling a current between the substrate and the electrode; controlling a current density on the substrate; controlling a deposition rate of the electrochemically reduced form of the metal ion on the substrate; rotating the substrate relative to the composition at a rate of rotation; or a combination thereof.

In some embodiments, the process includes controlling the rate of rotation from 10 revolutions per minute (rpm) to 500 rpm, specifically from 40 rpm to 400 rpm.

In a certain embodiment, the process includes oscillating substrate 6 relative to composition 30 at a rate of oscillation. The rate of oscillation can be control from 1 millimeters per second (mps) to 50 mps. Here, oscillating includes linearly oscillating substrate 6 relative to composition 30; rotationally oscillating substrate 6 relative to composition 30; or a combination thereof

Here, trench 12 is filled superconformally with metal from electrochemical reduction of metal ion 34 from bottom wall 16 toward top surface 9 and inwardly from side wall 14 toward a center of trench 12. The process controls the deposition rate within trench 12 to achieve uniform filling and avoid incorporating a defect (e.g., a void or seam) in superconformation 4.

In an embodiment, substrate 6 is contacted with composition 30, e.g., by immersing substrate 6 in composition 30 or spraying composition 30 on substrate 6. Accordingly, suppressor 36 and accelerator 38 can adsorb onto substrate 6. Without wishing to be bound by theory, it is believed that a differential in surface coverage of suppressor 36 occurs between top surface 9 and bottom wall 16 of trench 12. Accelerator 38 can accumulate at substantially uniform surface coverage over first surface 8, including the bottom wall 16 and side wall 14 of trench 12. Accelerator 38 can diffuse more rapidly than suppressor 36 so that an initial ratio of an amount of accelerator 38 to an amount of suppressor 36 within trench 12 can be relatively high to provide rapid deposition from bottom wall 16 and corner 18 of trench 12.

As formation of superconformation 4 continues, trench 12 fills with the metal, and a surface area within trench 12 decreases, the local surface coverage of accelerator 38 within trench 12 increases. Increased surface coverage of accelerator 38 within trench 12 maintains a control for deposition rate of the metal.

It has been found that composition 30 herein beneficially and advantageously provides. Here, the pH of composition 30 is alkaline so that suppressor 36, accelerator 38, and metal ion 34 are selected to reduce metal ion 34 to produce the metal at the alkaline pH to form superconformation 4 within trench 12 and on top surface 9 in an absence of a void within superconformation 4. Accordingly, composition 30 overcomes an ineffectiveness of a conventional additive (e.g., used in industrial copper superfill processing in an acidic electrolyte) to operate in alkaline electrolytes. Moreover, composition 30 is a resistive, alkaline electrolyte that provides for deposition of copper interconnects and to mitigate an iR potential drop arising from an electrically resistive copper seed layer, e.g., on substrate 6 (e.g., a 300 mm wafer). Further, composition 30 reduces corrosion of seed layer 44 that includes, e.g., Cu, Co, Mn, and the like.

Beneficially, composition 4 produces superconformation 4 in trench 12 having a selected width W or height H. Trench 12 can include a sub-micrometer width W, e.g., from 5 nm to 1000 nm.

Reduction of metal ion 34 can be conducted at a current density from less than 0.1 milliamperes to 10 milliamperes per square centimeter. Reduction of metal ion 34 to form superconformation 4 can be from less than 1 minute to 1 hour. Moreover, reduction of metal ion 34 can be performed using a direct, pulsed, or periodic current waveform applied to the electrode that can be a soluble or an insoluble or inert electrode material.

A wide variety of substrates 6 can be used with composition 30 such as a circuit board with vias or through-holes, integrated circuits, integrated circuits, and the like.

The articles and processes herein are illustrated further by the following Examples, which are non-limiting.

EXAMPLES

Example 1. Composition and electrochemical studies.

A composition for forming a superconformation on a substrate was prepared. The composition included an ethylenediaminetetraacetic acid (EDTA) complexed cupric sulfate electrolyte. The composition of the base electrolyte was 0.02 mol/L CuSO₄.2H₂O+0.04 mol/L C₁₀H₁₆N₂O₈, and the pH was adjusted to 12.0 through addition of sodium hydroxide.

Electrochemical and feature filling studies were conducted in a cell containing 60 mL of the composition. Studies were conducted with base electrolyte fabricated by separately dissolving cupric sulfate and EDTA in 18 MΩ.cm water followed by mixing to obtain the appropriate concentrations. The pH was adjusted through addition of NaOH. The electrolyte pH of 12.0 was determined using an electronic pH meter calibrated against buffer solutions of pH 7.0 and pH 10.0. The KSeCN was added to the cell in aliquots drawn from 2.6 mmol/L KSeCN solution prepared with 18 MΩ.cm water.

A rotating disk electrode (RDE) with diameter 0.95 cm (area 0.71 cm²) machined from oxygen-free-high-conductivity Cu was used for the additive and electrolyte studies. The side of the rod was passivated to emulate an RDE. The RDE was mechanically polished down to 1200/4000 grit silicon carbide paper and rinsed with 18 MΩ.cm water prior to each experiment.

Feature filling experiments were conducted on fragments of a general purpose patterned wafer (commercially available from ATDF) having a wide range of features sizes in both dense and isolated structures (“Q-Cleave-D”). Each piece was approximately 0.5 cm by 1 cm in size and included arrays of trenches ≈0.5 μm deep with widths ranging from more than 1 μm down to nearly 100 nm that were already coated with tantalum barrier and Cu seed. Arrays of all trench sizes could be found within regions spanning less than 1 mm along the specimen length. Depositions were conducted with the specimens in a horizontal position, the patterned side facing down. Clamped and contacted at one end, specimens were rotated around the vertical axis about that end (like a helicopter rotor blade) at the indicated rotation rates.

The trenches imaged were about 1 cm from the rotation axis, corresponding to a shear flow of the solution over the patterned surface at 10±3 cm/s at 100 rpm. The electrolytes were at room temperature (≈23° C.) under a covering flow of nitrogen during deposition. An Hg/Hg₂SO₄/saturated K₂SO₄ reference electrode (SSE) was used for all experiments and all quoted potentials are referenced to this scale. The reference electrode was connected to the working electrode compartment using a fritted salt bridge filled with a saturated solution of potassium sulfate. A platinum counter electrode was held in a frit-separated cell that was immersed within the main cell. Nitrogen sparging was used to remove dissolved oxygen prior to the experiments. Depositions were performed under potentiostatic control.

Impedance measurements were conducted for the cell geometry used in the electrochemical and trench filling studies. Consistent with the low metal ion concentration and the electrolyte pH, the resistance associated with deposition on the copper RDE was found to be significant, ranging between 36 Ω and 44 Ω depending on the alignment of the cell and RDE. Cyclic voltammetry (CV) is corrected for the associated iR drop as indicated, the corrections having an uncertainty of ±10% (e.g., ±4 mV for the 40 mV iR correction at 1 mA) based on the measured variation of cell resistance. Deposition on the patterned substrates was done without iR compensation due to control instabilities associated with the non-axisymmetric dies; deposition currents are provided for evaluation of associated iR loss.

Example 2. Trench filling.

FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D show examples of trench filling obtained in KSeCN additive-containing electrolyte. Defect-free, superconformal filling of the trenches is evident. Here, FIGS. 3A, 3B, 3C, and 3D show trenches cross-sectioned after copper deposition under the following conditions: deposition for 20 min at −1.3 V in electrolyte containing 2 μmol/L KSeCN while rotating at 100 rpm (FIGS. 3A and 3B); or deposition for 30 min at −1.3 V in electrolyte containing 2 μmolKSeCN while rotating at 40 rpm (FIGS. 3C and 3D). Applied potentials were not corrected for the iR drop across the ≈40 Ω cell resistance.

Feature filling exhibited accelerated growth from interior corners of features, bottom-up filling, and overfill bump formation shown in micrographs of FIGS. 4A and 4B. The superconformation shown in FIG. 4A was formed from accelerated deposition from the bottoms of features for 20 min deposition at −1.3 V in electrolyte containing 2 μmol/L KSeCN while rotating at 40 rpm. Similarly, the superconformation shown in FIG. 4B was formed from accelerated deposition from interior corners of features with deposition for 15 min deposition at −1.3 V including iR compensation in electrolyte containing 0.5 μmol/L KSeCN while rotating at 400 rpm.

FIG. 5 shows a micrograph of a dense array of trenches that exhibited deposition within a patterned region that had enhanced deposition toward a center of the array with superconformal filling of the trenches. Here, deposition occurred for 40 min at −1.3 V in electrolyte containing 1.5 μmol/L KSeCN while rotating at 40 rpm.

Example 3. Electrochemical voltammograms.

FIG. 6A shows linear sweep voltammograms obtained using the Cu RDE in the EDTA-Cu electrolyte for different KSeCN concentrations according to the composition described in Example 1. A KSeCN-free electrolyte exhibits suppressed deposition to approximately −0.6 V below the reversible potential, an example of the previously noted suppression in some complexed electrolytes. Substantial depolarization is induced by the additive (as is enhancement of dissolution positive of the reversible potential). In addition, while the positive-going return sweeps in the additive-free electrolyte exhibit a larger current density than the negative-going initial sweeps, the opposite occurs at higher additive concentrations. FIG. 6B shows CVs over a more limited potential range for rotation rates of 100 rpm and 400 rpm; the data for additive-free electrolyte and electrolyte containing 0.5 μmol/L KSeCN capture the impact of changing metal ion transport and additive transport, respectively.

More particularly, FIG. 6A shows the voltammetric measurement in electrolytes with the indicated KSeCN concentrations with scan rate 1 mV/s and RDE rotating at 400 rpm (early and steady state current densities from chronoamperometry are overlaid). Similarly, FIG. 6B shows the voltammetric measurement for additive-free electrolyte and electrolyte with 0.5 μmol/L KSeCN with 1 mV/s scan rate and RDE rotating at 100 rpm and 400 rpm. During data acquisition, the potentiostat compensated for 90% of the ≈40 Ω cell resistance.

Example 4. Chronoamperometry.

Chronoamperometry at applied potentials from −1.2 V to −1.5 V is shown for electrolyte with 0.5 μmol/L KSeCN additive in FIG. 7A. Data for electrolyte with 4 μmol/L KSeCN additive is shown in FIG. 7B. The RDE was rotated at 400 rpm for all data. Data for slower, 100 rpm RDE rotation rate (i.e., slower transport) is shown for electrolyte with 4 μmol/L KSeCN in FIG. 7C. In all three graphs, rising transients followed by stabilization at constant current suggest accumulation to saturation of an accelerating adsorbate on the deposit surface. Consistent with this interpretation, the rise time decreased by approximately an order of magnitude when the concentration of KSeCN increased by a factor of eight from 0.5 μmol/L to 4 μmol/L (FIGS. 7A and 7B). Increase of the rise time by approximately a factor of two when the rotation rate decreased by a factor of four (compare FIGS. 7B and 7C) doubled the boundary layer thickness. The values of the minimum (magnitude) current densities and the maximum (magnitude) steady state current densities in the chronoamperometry for the electrolyte with 4 μmol/L KSeCN (FIG. 7B) are overlaid on the slow scan rate CV data in FIG. 6A. The steady state current density at −1.5 V matches the value on the CV for 4 μmol/L KSeCN, and the early time current density at −1.5 V matches the value on the CV for additive-free electrolyte. However, the values deviate increasingly at less negative potentials; at −1.2 V the steady state value exceeded the current density in the corresponding CV at that potential by a factor of ≈2 while the early time value exceeded the current density in the CV for additive-free electrolyte by a factor of ≈4.

Example 5. Current Density.

FIG. 8A shows the current density recorded as the RDE is cycled between electrolyte containing 2 μmol/L KSeCN and additive-free electrolyte. The rising transients manifest the impact of accelerator adsorption in the additive containing electrolyte on the Cu deposition rate already seen in FIGS. 7. The falling transients manifest the impact of decreasing adsorbate coverage in the additive-free electrolyte, clearly indicating its consumption with time. The overlaid transients in FIG. 8B show the consistency of the adsorbate consumption from run-to-run. The deposition rate, and thus adsorbate coverage, was preserved during the transfer between the electrolytes; the comparatively small change in current upon transfer possibly reflects different (uncompensated) cell resistances.

In particular, FIG. 8A shows deposition current density as the RDE was switched from electrolyte containing 2 μmol/L KSeCN to additive-free electrolyte and back for three cycles, and FIG. 8B shows the current decays during deposition in the additive-free electrolyte, start times offset to permit overlay, and prediction based on adsorbate consumption model. Applied potential was −1.2 V and was not corrected for the iR drop across the ≈40 Ω cell resistance. Rotation rate was 40 rpm, and the RDE was rinsed with water before transfer from the additive-containing cell to the additive-free cell.

FIG. 9 shows deposition currents for specimens shown in FIGS. 3A, 3B, 3C, and 3D. Patterned specimen sizes vary so that relative deposition currents do not translate directly into relative current densities.

Example 6. Composition with pH 10.1.

The composition according to Example 1 was subjected to adjustment of pH=10.1, and a substrate was contacted with the composition at pH 10.1 to form a superconformation. Formation of the superconformation in the composition with pH 10.1 provided copper deposition on patterned specimens that was superconformal that exhibited a pronounced dependence on pattern size and density. FIGS. 10, 10B, 10C, and 10D shows micrographs of the superconformation of the filling viewed in cross-sectioned specimens.

While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation. Embodiments herein can be used independently or can be combined.

Reference throughout this specification to “one embodiment,” “particular embodiment,” “certain embodiment,” “an embodiment,” or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of these phrases (e.g., “in one embodiment” or “in an embodiment”) throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The ranges are continuous and thus contain every value and subset thereof in the range. Unless otherwise stated or contextually inapplicable, all percentages, when expressing a quantity, are weight percentages. The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including at least one of that term (e.g., the colorant(s) includes at least one colorants). “Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not. As used herein, “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.

As used herein, “a combination thereof” refers to a combination comprising at least one of the named constituents, components, compounds, or elements, optionally together with one or more of the same class of constituents, components, compounds, or elements.

All references are incorporated herein by reference.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means “and/or.” Further, the conjunction “or” is used to link objects of a list or alternatives and is not disjunctive; rather the elements can be used separately or can be combined together under appropriate circumstances. It should further be noted that the terms “first,” “second,” “primary,” “secondary,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). 

What is claimed is:
 1. A composition comprising: a solvent; a metal ion disposed in the solvent; an accelerator disposed in the solvent; and a suppressor disposed in the solvent, a pH of the composition being alkaline and effective to form a superconformation comprising a damascene deposit that comprises an electrochemically reduced form of the metal ion.
 2. The composition of claim 1, wherein the metal ion comprises a transition metal.
 3. The composition of claim 2, wherein the transition metal comprises copper, cobalt, manganese, silver, gold, or a combination comprising at least one of the foregoing transitions metals.
 4. The composition of claim 1, wherein the accelerator comprises an anion.
 5. The composition of claim 4, wherein the anion comprises sulfur, selenium, tellurium, oxygen, or a combination comprising at least one of the foregoing atoms.
 6. The composition of claim 5, wherein the anion comprises SeCN⁻.
 7. The composition of claim 1, wherein the suppressor comprises a polymer, a ligand, a halide, or a combination comprising at least one of the foregoing suppressors.
 8. The composition of claim 7, wherein the polymer comprises a functional group comprising a hydroxyl, sulfhydryl, carbonyl, amine, imine, amide, carboxyl, phosphate, sulfate, phenyl, halo, aldehyde, haloformyl, cyanate, nitrate, nitro, borono, or a combination comprising at least one of the foregoing functional groups.
 9. The composition of claim 7, wherein the ligand comprises a halide, an amide, an η²-alkene, CO, CS, CO2, CN, an amine, a nitrile, an isocyanide, a phosphane, an alkylidene, an alkyldiide, a nitrene, an imide, an oxide, an alkylidyne, an alkyltriide, an η³-allyl, an η³-enyl, an η³-cyclopropenyl, NO, an η⁴-diene, an θ⁴-cyclobutadiene, an η⁵-cyclopentadienyl, an η⁶-arene, an η⁶-triene, an Θ⁷-tropylium, an η⁷-cycloheptatrienyl, an η⁸-cyclooctatetraene, or a combination comprising at least one of the foregoing ligands.
 10. The composition of claim 9, wherein the ligand comprises a functional group that comprises hydrogen, alkyl, alkoxy, fluoroalkyl, cycloalkyl, heterocycloalkyl, cycloalkyloxy, aryl, aralkyl, aryloxy, aralkyloxy, heteroaryl, heteroaralkyl, alkenyl, alkynyl, NH₂, amine, alkyleneamine, aryleneamine, alkenyleneamine, and hydroxyl.
 11. The composition of claim 10, wherein the ligand comprises an aminocarboxylic acid, a lactate, a malate, a citrate, or a combination comprising at least one of the foregoing.
 12. The composition of claim 7, wherein the halide comprises iodide, chloride, or a combination comprising lease one the foregoing halides.
 13. The composition of claim 1, wherein the pH is greater than or equal to
 12. 14. The composition of claim 1, wherein the metal ion is complexed to a ligand.
 15. A process for forming a composition, the process comprising: disposing a metal ion in a solvent; disposing an accelerator in the solvent; disposing a suppressor in the solvent; and adjusting a pH of the composition to be alkaline and effective to form a superconformation comprising a damascene deposit that comprises an electrochemically reduced form of the metal ion.
 16. The process of claim 15, wherein the pH is greater than or equal to 12 after adjusting the pH.
 17. A process for forming a superconformation, the process comprising: contacting a substrate with a composition, the composition comprising: a solvent; a metal ion disposed in the solvent; an accelerator disposed in the solvent; and a suppressor disposed in the solvent; controlling a pH of the composition to be alkaline; and producing a damascene deposit on the substrate to form the superconformation, the damascene deposit comprising an electrochemically reduced form of the metal ion.
 18. The process of claim 17, further comprising disposing an electrode in the composition.
 19. The process of claim 18, further comprising: subjecting the substrate to a first potential; and subjecting the electrode to a second potential.
 20. The process of claim 19, further comprising controlling a potential difference between the first potential and the second potential.
 21. The process of claim 19, further comprising controlling a current between the substrate and the electrode.
 22. The process of claim 19, further comprising controlling a current density on the substrate.
 23. The process of claim 19, further comprising controlling a deposition rate of the electrochemically reduced form of the metal ion on the substrate.
 24. The process of claim 19, further comprising rotating the substrate relative to the composition at a rate of rotation.
 25. The process of claim 24, further comprising controlling the rate of rotation from 0 revolutions per minute (rpm) to 500 rpm.
 26. The process of claim 19, further comprising oscillating the substrate relative to the composition at a rate of oscillation.
 27. The process of claim 26, further comprising controlling the rate of oscillation from 0 millimeters per second (mps) to 50 mps.
 28. The process of claim 27, wherein oscillating comprises linearly oscillating the substrate relative to the composition.
 29. The process of claim 17, wherein the substrate comprises a trench.
 30. The process of claim 29, wherein the trench comprises a sub-micrometer width.
 31. The process of claim 17, wherein the metal ion is complexed to a ligand in the composition. 